1. Field of the Invention
The present invention relates to an oxynitride phosphor and a light emitting device using the same.
2. Description of the Background Art
A semiconductor light emitting element such as light emitting diode (LED) has an advantage of being compact, requiring little power consumption, and being capable of stably performing high-intensity light emitting. Moreover, a light emitting device for obtaining a visible light by combining a semiconductor light emitting element and a phosphor has an advantage of the semiconductor light emitting element, and furthermore, can emit a light having a color according to purpose of use such as white and therefore, can be utilized for a liquid crystal display, a light source for a back light of a mobile telephone or a personal digital assistant, a display device utilized for indoor or outdoor advertisement and so forth, an indicator of each of portable appliances, a light source for an OA (office automation) equipment, and so forth.
In Japanese Patent Laying-Open No. 10-163535, there has been disclosed a light emitting device in which a semiconductor light emitting element emitting a blue or blue-violet light and one kind or two kinds of phosphor(s) are combined. Here, the phosphor(s) is/are selected so that an emission color of the semiconductor light emitting element and an emission color of the phosphor(s) have a relation of complementary colors to each other and emit a light having a pseudo white color.
Moreover, in Japanese Patent Laying-Open No. 09-153644, there has been disclosed a dot matrix type display device in which a group III nitride semiconductor emitting an ultraviolet light having an emission peak wavelength of 380 nm is used as an exciting light source and which has three kinds of phosphor layers emitting three primary color lights of red, green, and blue, respectively.
Furthermore, in Japanese Patent Laying-Open No. 2002-171000, there has been disclosed a light emitting device emitting a white light by using a semiconductor light emitting element emitting a light having a wavelength of 390 to 420 nm and using a phosphor excited by emission from this semiconductor light emitting element. Here, the semiconductor light emitting element emits a light having low visibility by human and therefore, its color tone hardly changes even when the light emission intensity or the light emitting wavelength of the semiconductor light emitting element is fluctuated. Moreover, a light having a wavelength of 390 to 420 nm is difficult to damage a device component such as resin dispersing the phosphor(s) and also has little harmful effect on a human body.
As a material for phosphors, conventionally, oxide or sulfide has been widely used. However, in recent years, examples of phosphors of oxynitride or nitride has been disclosed in Japanese Patent Laying-Open No. 2002-363554, Japanese Patent Laying-Open No. 2003-206481, International Publication No. WO2005/019376, and Naoto Hirosaki, Rong-Jun Xie, Koji Kimoto, Takashi Sekiguchi, Yoshinobu Yamamoto, Takayuki Suehiro, and Mamoru Mitomo, “Characterization and properties of green-emitting β-SiALON:Eu2+ powder phosphors for white light-emitting diodes”, Applied Physics Letters 86, 211905 (2005), and Kyota Uheda, Naoto Hirosaki, Hajime Yamamoto, Rong-Jun Xie, “Red phosphors for warm white light-emitting diodes” 305th meeting digest of Phosphor Research Society, 2004, pp. 37-47. Most of these phosphors are excited particularly by a light having a wavelength of 390 to 420 nm and thereby, light emission can be obtained highly efficiently and additionally, the phosphors have high chemical stability and high heat-resistance, and also have excellent characteristics such as small fluctuation of emission efficiency due to change of operating temperature.
Moreover, in Japanese Patent Laying-Open No. 2004-244560, a light emitting device having the following construction has been disclosed. The phosphor (Ca0.93, Eu0.05, Mn0.02)10(PO4)6Cl2, the phosphor (Ca0.955Ce0.045)2(Si0.964Al0.036)5N8, and the phosphor SrCaSi5N8:Eu have emission peak wavelengths in a region of blue violet to blue series, in a region of blue green to green, and in a region of yellow red to red series, respectively. It is supposed that by mixed colors of lights from these phosphors, the emission color is shown in a white-based region.
It is known that among oxynitride phosphors, a JEM phase phosphor disclosed in International Publication No. WO 2005/019376 is a silicon oxynitride phosphor having a JEM phase, which is a crystal phase that is different from α-Sialon and β-Sialon, and the phosphor shows nonconventional emitting of an intensive blue light by exciting of a near ultraviolet radiation.
Moreover, in Japanese Patent Laying-Open No. 2004-071357, as a conventional technology corresponding to one embodiment of the present invention, there has been disclosed a light emitting device in which a semiconductor light emitting element, phosphors that are a red phosphor, a green phosphor, and a blue phosphor are placed in order and thereby resorption of lights emitted from the phosphors near the semiconductor light emitting element is suppressed.
Furthermore, in Japanese Patent Laying-Open No. 2004-331934, there has been disclosed a red phosphor La2O2S: Eu+Si in which powder reflectances in wavelengths of 450 nm, 545 nm, and 624 nm, which are wavelengths that are of red and shorter than that of red, are 84% or more, 94% or more, and 97% or more, respectively.